1. Field of the Invention
The present invention relates to a process for the analysis of a row transfer photosensitive device.
2. Description of the Prior Art
The prior art and in particular U.S. Pat. Nos. 4,430,672 and 4,506,299 assigned to THOMSON-CSF, discloses photosensitive devices whose analysis takes place by row transfer.
In general, these devices comprise a photosensitive area constituted by M rows of N photosensitive elements each. The photosensitive elements of the different lines are connected in parallel by conductive columns to a memory. This memory periodically ensures the transfer to a read register of the signal charges collected on a row of photosensitive elements and transferred to the columns. Moreover, the memory ensures the transfer to an evacuated drain of the parasitic charges on the columns before the signal charges from one of the rows reaches the columns.
Thus, in row transfer photosensitive devices, there is consequently a periodic repetition of the two following sequences:
a first sequence corresponding to the transfer to the memory of parasitic charges on the columns, before the signal charges reach the columns; PA1 a second sequence corresponding to the transfer to the memory of the signal charges from a row on the columns.
The problem is that in the time interval between a first and a second sequence, there is an accumulation on the columns of parasitic charges which are read during the second sequence, at the same time as the signal charges. These parasitic charges are due to smearing and particularly to the overflow of photosensitive elements as a result of too intense illumination and reference is made to the blooming.
It is pointed out that as the photosensitive elements of the different rows are connected in parallel by conductive columns, it is merely necessary to have one too intensely illuminated point which overflows for the column to which this element is connected to receive parasitic charges.
The present invention makes it possible to solve the above problem in a very simple and effective manner.